Impaired DNA damage response promotes atherosclerosis by enhancing cellular senescence and proinflammatory activation

Abstract Background DNA damage likely contributes to the pathogenesis and progression of atherosclerosis. Chemotherapy, radiotherapy and some DNA damage response (DDR) syndromes are known to increase atherosclerosis. However, causative links between DNA damage and atherosclerosis are yet to be established. Purpose The aim of this study was to investigate the role of impaired DDR in atherosclerosis. Methods and results Ku80, a DNA repair protein, -deficient apolipoprotein E knockout mice (Ku80+/− ApoE−/−) and ApoE−/m- mice were fed on high-fat diet for 4 weeks, and then oil red O staining was performed on their isolated aortas. Plaque area was significantly increased in Ku80+/− ApoE−/− mice. Immunohistochemical analysis of lesions from Ku80+/− ApoE−/− mice revealed enhanced accumulation of DNA double-strand breaks (DSBs). Similar results were obtained from Ku80+/− ApoE−/− mice fed on high-fat diet for 2 weeks which was considered as the early stages of atherosclerosis. mRNA levels of inflammatory cytokines such as IL-6 and MCP-1 in the aorta were significantly elevated in Ku80+/− ApoE−/− mice compared with those of ApoE−/− mice. To investigate whether impaired DDR is associated with the increased expression of inflammatory cytokines, vascular smooth muscle cells were isolated from Ku80 WT and Ku80+/− mice and subjected to quantitative RT-PCR analysis. mRNA levels of IL-6 and MCP-1 were significantly elevated in Ku80+/− cells. In addition, IκBα protein expression was significantly decreased in Ku80+/− cells, which suggested enhanced NF-κB activation in those cells. Immunofluorescent analysis revealed accumulation of DSBs and persistent DDR in Ku80+/− cells. In addition, elevated p16 mRNA level and senescence-associated β-gal activity were observed in Ku80+/− cells. Conclusion These results suggested that impaired DDR promoted atherosclerosis partly through cellular senescence and enhanced proinflammatory activation. Therefore, therapies targeting enhancing DDR may be beneficial in the prevention of DNA damage-induced atherosclerosis. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): KAKENHI